The Yale University researchers said follow-up studies will investigate how fructose affects the brain and eating behavior.

Fructose is found in fruits, vegetables, table sugar and many processed foods.

In experiments with eight healthy volunteers, the researchers said they found that fructose is converted in the brain from another simple sugar -- glucose.

"In this study, we show for the first time that fructose can be produced in the human brain," said study first author Dr. Janice Hwang, an assistant professor of medicine.

"By showing that fructose in the brain is not simply due to dietary consumption of fructose, we've shown fructose can be generated from any sugar you eat. It adds another dimension into understanding fructose's effects on the brain," Hwang said in a university news release.

In the brain, glucose sends signals of being full, but that's not the case with fructose. The conversion of glucose to fructose also occurs in other parts of the body, the researchers said.

"This pathway may be one other mechanism by which high blood sugar can exert its adverse effects," Hwang said.